There is a need for controlled release of substances in a variety of fields. One example of this is in the medical field where there is the need to time release ingested or injected drugs. There are several ways to effect the controlled and extended release of substances, such as through the use of matrix tablets, micro-capsules or coated pellets that are incorporated into hard gelatin capsules or enteric coated labels. Production processes include conventional granulation and tabletting of matrix tablets, pan coating, prilling, extrusion and spheroidization, fluid bed processes, spray drying, spray chilling, and coacervation.
In most controlled release devices, the active substance is surrounded by a polymer matrix which slowly dissolves on contact with aqueous media to release the active substance.